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EFHW Portable Antenna
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| Homer_2WR183 |
Posted on 03-01-2013 18:57
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Junior Member
Posts: 40
Joined: 12.12.12
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End Fed Portable Antenna
This describes the pictured EFHW (End Fed Half Wave) antenna in the photos below. The SWR achieved with this device was very low, 1.0:1 on the 11 meters band it was built for. Different setup locations can produce different results. I believe it could be used to tune for other bands as well. I used it as a portable, but it is in static base use now.
If interested, how to make the coil in the above photo.
Materials:
wire
wax paper
blue swimming pool flex hose
Hot glue.
1. Cut a section of this hose, cut it into strips.
2. Wax paper rolled and taped onto cylinder such as PVC pipe.
3. Hot glue strips of hose onto wax paper.
4. Wrap wire for coil around the form into the grooves.
5. Hot glue across all the blue hose strips.
6. Slide wax paper off of the PVC form, remove wax paper from within the coil.
The capacitor is:
1. three 3/4" x 1/8" x 3-1/2" long flat aluminum stock plates with
2. two strips of double sticky tape that has only
3. one side of the tape peeled away so it can stick to the bar it is on.
a. The coil and the cap are wire together parallel (each end wired together).
b. At one end the ground side (braid) of the coax is attached, and at the other end the antenna wire is attached.
c. The center conductor of the coax is fitted with a jumper and alligator clip so as to be used to tap the coil.
d. The coax attaches via a PL239 fitted to the backing.
e. Everything is mounted on a nonconducting backing. I have put some in a plastic pencil box, or a Tupperware box.
To tune.
1. Measure out the wire antenna for the band you want to work (the one in the photo work the world on 11 meters for a friend in Ft Worth, Texas as a stealth antenna in an HOA neighborhood)and attach it to the antenna as in the photos - the opposite end from the PL239 connection.
2. Clip the coil midway from each end with the alligator clip jumper wire.
3. Begin to adjust the sliding bars of the capacitor plates until you achieve the lowest possble match. Any means of temporarily holding them together can be utilized as long as it is non-conducting. I have used plastic potatoe chip bag clips, and wooden spring loaded clothes pins.
4. When the tune is as low as you can get it with the capacitor adjustment retap the coil at another spot until the tune comes down again.
Hopefully you are done by now, but if not continue to go back and forth with the cap/coil adjustments process until the job is done.
This capacitor can be built with only two cap plates, but three should give more control over a wider range of frequencies/bands.
In the photo can be see how the cap plates were hot glued to remain static for center frequency on US CB 11 meters band.
Edited by Homer_2WR183 on 03-01-2013 19:10
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My friends call me Homer |
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| Homer_2WR183 |
Posted on 03-01-2013 19:57
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Junior Member
Posts: 40
Joined: 12.12.12
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Thanks, Paul.
I did have fun with it.
Then a friend came by who I thought could use it.
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My friends call me Homer |
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| Homer_2WR183 |
Posted on 04-01-2013 03:28
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Junior Member
Posts: 40
Joined: 12.12.12
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This is an example of one I made in a plastic school supply box that I use since gifting the one above:
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My friends call me Homer |
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| 19LV001 |
Posted on 07-01-2013 23:42
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Admin
Posts: 6
Joined: 19.09.12
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Love this projects thanks for sharing, and you slogan It's not grazy, if it works lol... happy building |
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| Homer_2WR183 |
Posted on 08-01-2013 00:40
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Junior Member
Posts: 40
Joined: 12.12.12
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Glad you enjoyed it.
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My friends call me Homer |
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| 19LV002 PJ |
Posted on 10-01-2013 00:49
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Admin
Posts: 44
Joined: 15.09.12
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Nice idea love it, mabey i will make my self one for the porto!
thanks for sharing!
keep up the good work!!
73'
PJ |
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| Homer_2WR183 |
Posted on 10-01-2013 02:25
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Junior Member
Posts: 40
Joined: 12.12.12
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It's easy to do. Takes about an hour, but well worth it.
These are useful for a permanent base antenna, too.
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My friends call me Homer |
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| 19LV002 PJ |
Posted on 10-01-2013 14:24
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Admin
Posts: 44
Joined: 15.09.12
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will try it for shure and will upload here on the cluster! |
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| Homer_2WR183 |
Posted on 10-01-2013 18:13
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Junior Member
Posts: 40
Joined: 12.12.12
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I'll be looking for it.
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My friends call me Homer |
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